Improvement in valves for steam-pumps and engines



'NITED STATES PATENT OFFICE.

WILLIAM B. SNOW, OF BROOKLYN, NEW YORK.

IMPROVEMENT IN VALVES FOR STEAM-PUMPS AND ENGINES.

Specication forming part of Letters Patent No. 118,064, dated August 15, 1871 antedated August 3, 1871.

To all whom t may concern:

Be it known that I, WILLIAM B. SNOW, of Brooklyn, in the county of Kings and State of New York, have invented a new and useful Improvement in Valves for Steam-Pumps and Engines; and I do hereby declare that the following is a full, clear, and exact description, reference being had to the accompanying drawing forming part of this speciiication, and in which- Figures l and 2 represent longitudinal sectional views of a valve, constructed in accordance with my invention, arranged within the steam-chest of an engine or steam-pump and over ports or passages connected with the cylinder of the steam or en gine-piston, said views showin g the valve in different working positions. Fig. 3 is a transverse section through the central portion of the valve.

Similar letters of reference indicate corresponding parts.

My invention relates to valve arr. ngements in which the direct action of the steam is used to complete the throw of the valve that controls the movement of the main or steam-piston. rIhe invention consists in a main valve in direct connection with a main stem, and constructed for operation in combination with fixed pistons and suitable surfaces, ports, and passages, whereby the following leading peculiarity in the action of said valve is obtained: The valve, being started or closed by a tappet motion connected with the main or engine-piston, ha-s its throw completed, to effect the reversal of said piston, in an accelerated manner, by the direct action of the steam on the one and the same main valve, and without the aid of a detached moving piston or supplementa-ry valve. Provision also is made whereby said valve, toward the end of its stroke, so closes a passage which connects with the exhaust that an air-cushion is produced to arrest the accelerated motion of the valve.

Referring to the accompanying drawing, Arepresents the valve-chest, to which steam is admitted by an inlet, b 5 and B is the main valve, arranged to control, as it is slid backward and forward, the ports or passages c c that connect with the opposite ends of the steam-piston cylinder, and which are alternately brought into communication with the steam-space of the valvechest and with a general exhaust-passage, d. This valve B, which is provided with a main stem, e,

has its face f preferably constructed of a double D -form, and the seat over which it slides recessed at its ends to allow the steam from the valvechest to pass under it to the D-cavities g g' in the valve, which latter has its central portion h, that divides said cavities, constructed to slide over the bridges t' t' between the exhaust and steam-ports of the working cylinder. The back of the valve has mounted on it, so as to form part of it, two opposite-end cylinders, k lo which are connected by an intermediate smaller cylinder, l. These several cylinders are tted or provided with stationary pistons m m and a on 011e and the same rod to correspond, and the length of the larger cylinders 7c k', which are open at their outer ends, is such that during the reciprocating action of the valve said cylinders are made to slide on and off, alternately, their respective stationary pistons m m', or otherwisemade to open and close passages for the steam into the cylinders k k. The smaller cylinder has an exhaust branch, o, arranged to project interlnediately of its length down through the central portion It of the valve. The piston a in said cylinder may, from the function which it performs, be termed an exhaust-piston.

The operation of the valve is as follows: The tappet motion of the engine or steam-piston of the pump alternately acts, toward the close of said pistonls stroke, upon the valve in reverse directions, to close its face portion f relatively to the steam or steam and exhaust-ports c c and d, and at the termination of such closing action to slightly uncover either one end cylinder 7c or 7c from off its stationary piston m or m', also to establish communication through the exhaust branch 0 between the opposite one of said cylinders e nd the general exhaust d. This is the position of the parts shown in Fig. 2 of the drawing, where the valve, starting from the position shown in Fig. l, is supposed to he moving in direction of the arrow x. The valve having been started by the tappet motion to the position indicated in Fi. 2, steam rushes from the valve-chest into the cylinder or chamber 7c', to continue, by direct action or pressure, the throw of the valve in the direction of the arrow, and which it does with an accelerated motion, thus suddenly opening the valve as regards the control of the portsc c and'd. Toward the termination of such stroke, however, the exhaust branch o is brought over the bridge i, which thus is made to close communication between the cylinder k and general exhaust d, there by forming' an air-cu shion in said cylinder to check the accelerated motion ofthe Valve and to arrest the latter in its reversed position. Alike action takes place in au opposite movement of the valve under a reversed exposure of the cylinders 7c L" to the steamspaee of the valve-chest, and7 by the changed position of the branch o relatively with the small piston a to the general exhaust d, until an air-cushion is established in the cylinder k in like manner as already described with reference to the cylinderl lo.

Wha-t is here claimed7 and desired to be secured by Letters Patent, is

1. The combination, with the main slide valve, of its attached cylinders k 7a and smaller cylinder I, together with their respective stationary pistons ml and m and exhaust-piston a, substantially as specified. i

2. The combination of the exhaust-piston a with the'exhaust branch o in the valve, essentially as specifi ed.

3. The exhaust branch o in the valve, in combination with the bridge i between the exhaust and steam-ports of the engine or pump7 and with the cylinders k k and Z and stationary pistons m m and fn, essentially as and for the purpose herein set forth.

4. The valve B, formed with two D-cavities g g', in combination with the exhaust branch o, the cylinders 7c 7c and l, and the stationary pistons m m and a, substantially as shown and described.

Witnesses: W. B. SNOW.

FRED. HAYNES, R. ERABEAU. 

